**4.4 Intensity of mixture**

Several studies proved that the intensity of mixture in an CSTR digester has an effect on the process inhibition and the re-establishment of the organic overload (Hill & Bolte, 1989). Other researchers (Hill, 1990) studied the accumulation of acetate and propionate in a CSTR digester which treats municipal solid waste and the biosolides with an aggressive starting and an organic overload. They noted that while acetate was consumed thereafter, propionate persisted in the whole system and it started to decrease only after the reducing of mixture intensity. They also noted that a digester with a reduced mixture can tolerate a higher organic load than the digester with an intensive mixture.
